The TeX Catalogue License Definitions: OTHER-FREE

other-free: free license not otherwise listed, or more than one
free license applies

This license statement is used in two distinct circumstances.
Either the
software is covered by a license that does not fit into
any of the “formally” specified categories, but the
catalogue team judges it
usable by most users. Otherwise, the software consists of distinct
parts to which different (free) licenses apply.

While use is probably safe, each potential user should
check the software’s license statement (or statements) before
using the software.